Railroad hopper cars are commonly used to economically transport commodities between distantly spaced geographic locations. Dry granular commodities can be rapidly discharged from the hopper car through gate assemblies mounted in material receiving relation relative to standard openings on a bottom of the hopper car. Each gate assembly typically includes a frame defining a discharge opening. A gate is slidably movable on the frame and a drive mechanism is provided for moving the gate between closed and open positions. In a closed position, the gate prevents discharge of the commodity from the hopper car. When the gate is opened, the commodity is gravitationally discharged through the discharge opening defined by the gate assembly.
Hopper cars typically include a mounting flange provided about each standard opening on the bottom of the hopper car. Such hopper car mounting flanges typically define a series of apertures or openings arranged in a generally standard bolting pattern. The gate assembly frame includes, toward an upper end thereof, a mounting flange designed to facilitate securement of the gate assembly to the hopper car. A transition wall section angles inwardly from the mounting flange on the gate assembly frame toward the discharge opening for the gate assembly.
Once a hopper car reaches an unloading site, the gate on the gate assembly is opened and gravity causes the commodity within the walled enclosure or hopper on the car to freely drop from the railcar's hopper through the discharge opening and into a take-away device. There are several common options for the take-away device. One option involves an open-pit having conveyance equipment, i.e., a belt-conveyor or pneumatic conveyor arranged toward a bottom thereof. A second option involves a sealed pit using unloading “boots.” With this device, a boot is raised from beneath and between the rails and seals against a “boot flange” on the bottom of the gate assembly. During discharge, the commodity falls from the hopper, passing into the boot, from whence the commodity is directed toward and deposited onto conveyance equipment under the rails. These unloading boots are available in several standard sizes.
Another common option for directing a discharged commodity from the hopper car involves use of a portable unloading sled having a selectively operable conveyor. Unlike unloading pits, which are more or less permanently located, portable unloading sleds allow unloading of the railcar at almost any location where the railcar can be safely parked and accessed. These portable unloading sleds are specifically designed to fit between the top or upper surface of the rails and the bottom of the discharge gate assembly. To reduce the commodity lost during discharge and transfer of the commodity, the portable sleds seal against the “boot flange” on the bottom of the gate assembly.
Prior to the discharge of commodity from the railcar, the portable unloading sled is wheeled or otherwise moved into place on top of the rails and under the discharge outlet of the gate assembly. The conveyor is engaged or otherwise “turned ON” and the gate of the gate assembly is thereafter opened. The unloading sled serves to convey the commodity received from the hopper of the railcar into silos, truck-trailers, or is simply deposited onto the ground.
To reduce their costs while adding versatility to railcar usage, railroad car builders and manufacturers desire a railcar having a discharge gate assembly which is suitable for use with and promotes unloading of the hopper car using either unloading “boots” and/or portable sled unloading devices. Many factors and design considerations, however, converge to make the railcar manufacturer's wants and desires difficult to accomplish.
A railcar hopper car discharge gate assembly design is complicated considering portable unloading sleds require a certain amount or degree of clearance between the top or upper surface of the rails and a lowermost surface on the lower or “boot” flange on the gate assembly. Adding complexity to the gate design is the fact railcar builders and manufacturers have been designing the gate assembly mounting flange on the bottom of the railcar as low as possible. Such a car design advantageously increases the cubic capacity of the railcar while also beneficially lowering the center of gravity of the car.
Bolting a standard and heretofore known gate assembly to the lowered mounting flange on the railcar unfortunately results in insufficient rail clearance for safe movement of the railcar over vertical curves and related track equipment, i.e., switches and the like. Moreover, bolting a standard and heretofore known gate assembly to the lowered mounting flange on the railcar does not provide sufficient space and clearance whereby allowing a portable unloading sled to fit between the upper surface of the rails and a lowermost surface on the lower or “boot” flange on the gate assembly.
Designing a railcar discharge gate assemblies with an overall reduced height which allows use of a portable unloading sled would appear relatively simple until a closer examination of such a drastic design change is carefully and fully analyzed. Changing the geometry of the railcar discharge gate results in a gate assembly having a discharge opening and “boot flange” which is too large for standard unloading boots. In other words, as the overall height of the gate assembly is shortened, the overall size of the discharge opening of the gate assembly gets bigger to a point whereat it is too large for standard unloading boots.
For example, railroad hopper car discharge gate assemblies have been designed with an overall height of about 7.0 inches so as to allow a portable unloading sled to fit between the top or upper surface of the rails and the underside of the “boot flange” on the railcar discharge gate assembly. The “boot flange” opening on one such exemplary gate, however, measures about 26.5 inches by 56 inches or about 1484 square inches. The “boot flange” opening on another of such exemplary gates measures about 25.25 inches by about 59 inches or about 1490 square inches. In either example, the “boot flange” opening on the gate assembly is simply too large for the standard nominal 13 inch by 42 inch unloading boot (having outside dimensions of about 19 inches by 48 inches) to adequately seal therewith and thereagainst. As a result, and when such gate assemblies are used in operable combination with the standard 13 inch by 42 inch boot, commodity being discharge from the railcar readily spills outside of the boot and is lost—a result not viewed favorably by the customer.
To further complicate the gate assembly design, the Association of American Railroads (the “AAR”), revised the Standard governing locking systems for gate assemblies used on hopper-type railroad cars. The revised Standard (S-233-2011) requires the locking/unlocking or latching/unlatching functions for the gate assembly to be integrated into the discharge gate operating mechanism. As such, rotation of a capstan in a direction to open the gate must first unlock or unlatch the gate and then move the gate from the closed position to the open position.
Thus, there is a continuing need and desire for a railcar discharge gate assembly offering adequate clearance beneath the car and which can be used with a conventional portable unloading sled and has an opening through which commodity passes which also allows use with a standard unloading boot and, more specifically, the size boots used in 13 inch by 42 inch outlet gates while satisfying the latest AAR Standard.